The present invention relates to improvements in welding robots, and more particularly in arc welding robots for use in inert gas metal arc welding (xe2x80x9cMIGxe2x80x9d), active gas metal arc welding (xe2x80x9cMAGxe2x80x9d) and tungsten inert gas arc welding (xe2x80x9cTIGxe2x80x9d) and variants.
Welding robots are programable machines designed to perform a variety of welding functions. Unlike welding machines that are custom built to perform a specific function, welding robots need to be designed to provide for significant freedom of movement and placement of the tip of the welding nozzle. To facilitate this freedom of movement and positioning, welding robots traditionally use a series of arms and motorised rotatable joints which when used in combination allow movement of the welding nozzle in three dimensions. The electrical current, shielding gas and welding wire are generally supplied to the welding nozzle by means of a co-axial cable.
Two disadvantages of the prior art are that movement of the robot results in wear on the coaxial cable and the co-axial cable may impinge on the robot""s freedom of movement. For example, when the robot is programmed to perform circular welding the co-axial cable may have to flex to pass underneath an arm of the robot. This causes wear and damage to the cable and may restrict the movement of the robot. Such cables are often expensive to replace.
It is an object of the present invention to provide improvements in welding robots to avoid the disadvantages of the prior art by reducing the wear and tear on welding cables and to reduce the restriction of movement caused by use of co-axial welding cables or to at least provide the public with a useful choice.
In a first aspect the present invention consists in a welding robot which includes a welding nozzle, said welding nozzle containing, or being adapted to contain, a welding electrode; an electrical slip-ring assembly with slip-rings mutually rotatable about a common concentric axis and conductively connected, or being adapted to be conductively connected, to said welding electrode; said welding nozzle being coupled to, or being adapted to be coupled to a flexible gas supply tube; said electrical slip-ring assembly being connected to, or being adapted to be connected to, an electrical power supply cable; said slip-ring assembly feeding electrical power to said welding electrode in use from said supply cable with said cable remaining in a substantially fixed position when said welding nozzle is caused to rotate about said axis.
In a second aspect the present invention consists in a welding robot which includes a welding nozzle, a welding electrode contained within said nozzle; mounting means rotatable about an axis, an electrical slip-ring assembly with slip-rings mutually rotatable about said axis, which is a common concentric axis, and conductively connected to each other and to said welding electrode, said slip-ring assembly being insulatingly mounted on said mounting means; said welding nozzle being coupled to a flexible gas supply tube; said electrical slip-ring assembly being connected to an electrical power supply cable; said slip-ring assembly feeding electrical power to said welding electrode in use from said supply cable with said cable remaining in a substantially fixed position when said welding nozzle is caused to rotate about said axis.
In a third aspect the present invention consists in a welding robot in which the power supply to the electrode is fed via a slip-ring assembly.
In a fourth aspect the present invention consists in a method of robotic arc welding which includes the step of feeding electrical current to the welding electrode via a slip-ring assembly which shares a common axis with one of the axes of rotation of the robot.
In a fifth aspect the present invention consists in a welding robot including a power cable connected or connectable to a welding electrode within a welding nozzle via a slip-ring assembly integrated with but electrically insulated from a rotatable joint of the robot and a gas tube connected to said welding nozzle.
In a sixth aspect the present invention consists in a slip-ring assembly comprising an insulating mounting member for attachment to a welding robot in use, conductive slip-rings held on the mounting member for mutual rotation about an axis which in use coincides with an axis of rotation of the robot, attachment means for an input power cable on one slip-ring, means for feeding power from the other slip-ring to the welding electrode in use, and compression means to hold the slip-rings in mutual electrical contact.